One of the principal drawbacks related to keeping beverages at their proper serving temperature is the tendency for such beverages to assume the ambient temperature in the environment into which they have been placed. A hot beverage, such as coffee or tea, particularly when served in an uninsulated cup, quickly cools. A cold beverage, such as an iced soda, quickly warms to room temperature, causing the ice to melt and dilute the beverage.
Various solutions to this problem have been proposed, which act passively to maintain the temperature of the beverage through some kind of insulation. For example, an insulated foam or fiberboard cozy can surround the beverage container, helping the container to retain its heat or to slow the infiltration of heat into a cold beverage. These passive systems slow the process of heat transfer, but they do not eliminate it or compensate for it entirely.
On the other hand, several active heat management systems have been developed, which for space and safety purposes make use of a Peltier or thermoelectric device. Such devices are well known in the art to which the present invention relates and consist essentially of a pair of ceramic plates separated by an array of cubes of bismuth telluride or a similar material. When a direct current is applied across the device, heat is moved from one side of the device to the other, producing a cooling effect on one side of the device. If the polarity of the current is reversed, the device becomes an efficient heater. Such devices are generally more efficient at cooling in combination with a heat sink, and because of the polarity-reversing feature of these devices, they are suitable for use where selective heating and cooling operations are desired.
For example, in U.S. Pat. No. 5,042,258, an insulated mug is provided with a heat-conductive bottom inner surface and a thermoelectric device in the base of the mug. The base of the mug is provided with heat-conductive fins, and the thermoelectric device, when energized, acts to heat or to cool the container, depending on the polarity of the current. In another example, in U.S. Pat. No. 6,141,969, a cupholder is provided with a thermoelectric device in a similar orientation, with a finned base and insulated sides.
One of the drawbacks of these designs is the orientation of the thermoelectric device—namely, at the bottom of the cup or cupholder. This orientation is presumably chosen for two reasons. First, in such an arrangement, the cup or the liquid can be reasonably guaranteed to be in physical contact with the thermoelectric device, which contact aids in the heat transfer as any air between the thermoelectric device and the cup or liquid acts as an insulator, reducing the efficiency. Second, because at least for cooling operations it is necessary to place fins against the heat sink, the ability to place the fins appropriately affects the arrangement of the device members.
However, the placement of the thermoelectric device at the bottom of the cup or holder poses the problem of uneven heating or cooling of the contents. Because the portion of the beverage next to be consumed is farthest away from the thermoelectric device, that portion receives very little benefit from the use of the device. Additionally, uneven heating of a hot beverage could cause the liquid at the bottom to become overheated, resulting in a burn injury to the drinker if the heat does not adequately diffuse through the liquid, or, at a minimum, an unpleasant taste if the beverage burns.
Moreover, the placement of the thermoelectric device at the bottom reduces the surface area of the contact between the cup or liquid and the heating or cooling surface. This surface area is further reduced because bottoms of beverage containers are rarely uniformly flat; most have bottoms that are shaped for efficient movement through a conveyor system or for stability. A greater heat-conductive surface area results in a more even and efficient cooling or heating process. When the thermoelectric device is oriented at the bottom of the container, the surface area of the contact is typically far smaller than the area of the non-heating, non-cooling surface.
Conventional cupholder systems also lack the ability to expand or contract to fit cups and containers of various sizes and profiles, such as cylindrical cans and frusto-conical coffee cups having pitched sides. Because these systems do not expand or contract to meet the cup size, they do not maintain solid, heat-conductive contact with the cup.
What is needed, then, is an active heat management system that makes use of thermoelectric technology more effectively than conventional systems, and that maintains better heat-conductive contact with the cup of liquid than conventional cupholder systems, particularly in the context of containers of varying sizes.